In conventional tape cartridges used as storage media that are employed in external storage units for computers, etc., there is known a type in which magnetic tape is wound on a single reel and this reel is rotatably housed within a cartridge case. This magnetic tape is employed as a data storing tape for computers, etc., and because important information is stored, reel-rotation restraining means to restrict rotation of the reel is installed so that problems, such as tape jamming, etc., do not occur and so that the magnetic tape is not forwarded unexpectedly when not being used, such as when being archived, etc.
The reel-rotation restraining means is equipped with a restraining member that restricts rotation of the reel by engaging part of the reel, and is provided so that when the cartridge is loaded into a drive unit such as an external storage unit, etc., a restrained state by the restraining member is released according to a reel chucking operation performed by drive-side rotation drive means.
Hence, due to demands for enhancement in the reliability of the aforementioned operation of the reel-rotation restraining means, prevention of dust entry into the cartridge, etc., this reel-rotation restraining means is provided in a structure separated into a restraining member for restricting rotation of the reel, an urging member for urging this restraining member in a restraining direction, and a releasing member for moving the restraining member in a releasing direction by moving in accordance with the chucking operation of the drive-side rotation drive means.
That is, in the non-operative condition, the reel is restricted by the restraining member so that it does not rotate unexpectedly, as a result of which the magnetic tape is not forwarded. However, if the cartridge is loaded into a drive unit and chucking of the reel is performed by rotation drive means, the releasing member moves in interlock with the chucking operation and releases the restraining member. In this state, the reel is rotatable and therefore the magnetic tape can be forwarded and rewound.
In the aforementioned mechanism, it is also preferable to perform the pushing operation, for the releasing movement of the releasing member which results from the chucking operation of the drive-side rotation drive means, at a plurality of positions on the outer peripheral portion rather than at a single position on the center portion, because a stable releasing operation can thus be performed. At this time, it is advantageous in achieving structural simplification, etc., to provide a reel gear, which meshes the driving gear of the drive-side rotation drive means, in the reel, to provide pushing-up portions, formed in part of the releasing member, so that the distal ends abut the driving gear through the through holes provided in the real gear, and to provide the driving gear so that when the drive-side rotation drive means performs the chucking operation, the driving gear pushes the pushing-up portions and releases the releasing member.
However, piercing the reel gear and boring the through holes, as described above, will reduce the mesh between the reel gear and the driving gear and therefore become a problem with respect to driving the reel reliably. If the through hole is reduced from such a respect, the shape of the portion of the releasing member inserted into this through hole will also become smaller and therefore there is a possibility that it will become unstable for the tooth edge of the driving gear to abut the reduced portion accurately and give a reliable pushing operation.
In addition, in the case where the pushing-up portions are formed in part of the releasing member and are inserted into the through holes of the reel and slid, as described above, the releasing member is subjected to the urging force of the urging member and gives rise to bending deformation. As a result, since a tilting force acts on the push-up portion, part of the outside surface is pushed against the inner surface of the through hole and the friction resistance becomes greater, the sliding between the pushing-up portion and the through hole is disturbed, and there is a possibility that the releasing member will not be able to release the restraining member reliably.
The present invention has been made in view of the above-mentioned points, and accordingly, the object of the invention is to provide a magnetic tape cartridge in which the releasing member of the reel-rotation restraining means is capable of performing a reliable releasing operation.